Rollup merge of #41012 - durka:vis-matcher, r=petrochenkov

:vis matcher for macro_rules

Resurrection of @DanielKeep's implementation posted with [RFC 1575](https://github.com/rust-lang/rfcs/pull/1575).

@jseyfried was of the opinion that this doesn't need an RFC.

Needed before merge:

- [x] sign-off from @DanielKeep since I stole his code
- [x] feature gate
- [x] docs

2 files changed, 5 insertions, 1 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 3b928ea93c7..31669e1bbe3 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -5056,7 +5056,9 @@ impl<'a> Parser<'a> {
     /// and `pub(super)` for `pub(in super)`.  If the following element can't be a tuple (i.e. it's
     /// a function definition, it's not a tuple struct field) and the contents within the parens
     /// isn't valid, emit a proper diagnostic.
-    fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
+    pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
+        maybe_whole!(self, NtVis, |x| x);
+
         if !self.eat_keyword(keywords::Pub) {
             return Ok(Visibility::Inherited)
         }
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 74aa3984a9a..25cabef70c1 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -363,6 +363,7 @@ pub enum Nonterminal {
     /// Stuff inside brackets for attributes
     NtMeta(ast::MetaItem),
     NtPath(ast::Path),
+    NtVis(ast::Visibility),
     NtTT(TokenTree),
     // These are not exposed to macros, but are used by quasiquote.
     NtArm(ast::Arm),
@@ -392,6 +393,7 @@ impl fmt::Debug for Nonterminal {
             NtGenerics(..) => f.pad("NtGenerics(..)"),
             NtWhereClause(..) => f.pad("NtWhereClause(..)"),
             NtArg(..) => f.pad("NtArg(..)"),
+            NtVis(..) => f.pad("NtVis(..)"),
         }
     }
 }